Drycells: Cell-Suspension Micro Liquid Marbles for Single-Cell Picking.

Cell-picking technology is essential for cell culturing. Although the recently developed tools enable single-cell-level picking, they rely on special skills or additional devices. In this work, a dry powder that encapsulates single to several cells with a >95% aqueous culture medium, thereby acting as a powerful cell-picking tool, is reported. The proposed "drycells" are formed by spraying a cell suspension onto a powder bed of hydrophobic fumed silica nanoparticles. The particles adsorb to the droplet surface and form a superhydrophobic shell, which prevents the drycells from coalescence. The number of encapsulated cells per drycell can be controlled by adjusting the drycell size and cell-suspension concentration. Moreover, it is possible to encapsulate a pair of normal or cancerous cells and create several cell colonies within a single drycell. A sieving process can be used to sort the drycells according to size. The size of the droplet can range from one to hundreds of micrometers. The drycells are sufficiently stiff to be collected using tweezers; however, centrifugation separates them into nanoparticles and cell-suspension layers, with the separated particles being recyclable. Various handling techniques, such as splitting coalescence and inner liquid replacement, can be used. It is believed that the application of the proposed drycells will greatly improve the accessibility and productivity of single-cell analysis.